Deformation rate estimation on changing landscapes using. Abstract Title. Temporarily Coherent Point InSAR. Author name

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1 Deformaton rate estmaton on changng landscapes usng Abstract Ttle Temporarly Coherent Pont InSAR Le Zhang (1), Xaol Dng (1) and Zhong Lu (2) Author name (1)The Hong Kong Polytechnc Unversty, Kowloon, Hong Kong (2)U.S. Geologcal Survey, Vancouver, Washngton, USA Co authors names

2 Background Stable vs. Changng Landscapes On stable landscapes there are abundant scatterers that can keep vsble durng a long observaton tme span 1954 New York 1985 In well developed urban areas, dense persstent scatterers can be dentfed 2009

3 Background Stable vs. Changng Landscapes However on changng landscapes there are abundant scatterers that cannot keep vsble durng a long observaton tme span 1990 Duba 2003 In developng urban areas, persstent scatterers cannot be densely dentfed 2007

4 2007 Background Most developng countres are undergong surprsngly fast urbanzaton Urban renewal and sprawl Shangha 1990 Townscapes have changed sgnfcantly, rasng dffcultes for current MT InSAR technques to get detaled defo. maps Bangkok

5 Background Persstently Coherent Pont vs. Partally Coherent Pont Persstently Coherent Pont Vsble over the whole observaton tme span (year) Partally Coherent Pont Vsble over a part of observaton tme span (year)

6 Background Can we dentfy both persstently coherent ponts and partally coherent ponts smultaneously and retreve deformaton relably from these ponts?

7 Temporarly Coherent Pont InSAR Temporarly Coherent Pont not necessary to keep coherent durng the whole tme span ncludng persstently coherent pont and partally coherent pont t t (Courtesy of A. Hooper)

8 Temporarly Coherent Pont InSAR TCP dentfcaton: Image par based methods Offset devaton [1] Durng the coregstraton procedure, standard errors of the estmated offsets from strong scatterers s less senstve to the wndow sze and oversamplng factor used n the mage cross correlaton compared wth those from dstrbuted scatterers [2]. OT ot j1 ot j2 ot j jn std( OT ) 0.1 j Coherence map Sutable for mage pars wth short baselnes (spatal, temporal and Doppler) Coherence s used as threshold to select partally coherent ponts n [3][4] [1] Zhang, L., Dng, X.L., & Lu, Z. (2011a). ISPRS Journal of Photogrammetry and Remote Sensng, 66, [2] Bamler, R., & Eneder, M. (2005). IEEE Geoscence and Remote Sensng Letters, 2, [3] Bggs, J., Wrght, T., Lu, Z., & Parsons B. (2007). Geophyscal Journal Internatonal, 170, [4] Bggs, J., Burgmann, R., Freymueller, J.T., Lu, Z., Parsons, B., Ryder, I., Schmalzle, G., & Wrght, T. (2009). Geophyscal Journal Internatonal, 176, TCP: keep coherent n more than **% mage pars (say, 70%) We exactly know n whch nterferogram the selected TCPs are coherent.

9 Temporarly Coherent Pont InSAR TCP dentfcaton: Image based method Ampltude Mad Medan Rato (AMMR) v A m A v Mad A Medan A pont wth scaled ntensty tme seres (25): A Medan absolute devaton Mad(X)=medan(abs(X medan(x)) [0.1, 0.2, 0.2, 0.3, 0.2, 0.2, 0.3, 0.8, 0.85, 0.9, 0.9, 0.92, 0.92, 0.91, 0.94, 0.93, 0.95, 0.95, 0.92, 0.94, 0.92, 0.91, 0.91, 0.92, 0.93]; A Mad A v 0.45 v 0.03 Medan m A We do not know n whch nterferogram the selected TCPs are coherent. A PS? No; TCP? Yes!

10 Temporarly Coherent Pont InSAR TCP Parameter Estmator To resolve DEM error and lnear deformaton rate wthout the need of phase unwrappng Observatons are dfferental phases at the arcs (pont pars) n mult master nterferograms wth short baselnes Core algorthms: L 2 norm (least squares) estmator wth ambguty detector[5] L 1 norm estmator [5] Zhang, L., Dng, X.L., & Lu, Z. (2011b). IEEE Transactons on Geoscence and Remote Sensng, 49,

11 Temporarly Coherent Pont InSAR The system of observatons l, m topo, l, m defo, l, m atmo, l, m orbt, l, m nose, l, m 4 4 V M defo,, l m rl, m ( tj tj 1) vj js 4 B,, lm topolm,, h lm, rlm, snlm, h lm, lm, h V w w lml,, ', m' lm, lml,, ', m' lml,, ', m' l, m, l ', m' atmo, l, m, l ', m' orbt, l, m, l ', m' nose, l, m, l ' m' 1 Wrapped phases!! For each arc, we have h A V lml,,, m 1 2 I lml,,, m lml,,, m lml,,, m 1 2 I lm, lm, lm, 1 2 W A W w w w I 1 2 I lml,,, m lml,,, m lml,,, m How to resolve the parameters? T T

12 Temporarly Coherent Pont InSAR L 2 norm (least squares) estmator wth ambguty detector Ths algorthm s sutable for TCPs dentfed by mage par based methods Snce we exactly know n whch nterferograms the selected TCPs keep hgh coherence, we can get a coherence ndex for each TCP For each arc, only nterferograms n whch both ponts keep coherent are selected. hˆ Vˆ lml,,, m T dd 1 T dd AP A AP ˆ A A P A A P T dd 1 T dd T dd 1 T dd r A A P A A P mght have phase ambgutes!!

13 Temporarly Coherent Pont InSAR L 2 norm (least squares) estmator wth ambguty detector Ambguty detector Q ˆ ˆ A( A P A) A T dd 1 T dd Max( r ) c Max(( Q ) ) 2 Max(( Q ˆ ˆ ) ) TCP parameters After removng modulo 2p arcs, perform Arc Pont ntegraton LS resduals can tell us whether the arc has ambguty or not!

14 Temporarly Coherent Pont InSAR L 1 norm estmator For TCPs selected by mage based approach, we do not exactly know n whch nterferograms the TCPs are coherent When takng all nterferograms as observatons, we need to desgn a robust estmator to suppress the effect of outlers (.e., decorrelated phases and phase ambgutes at arcs) L 1 norm estmator s a good choce snce t s less senstve to outlers than LS Wth L 1 norm estmator, we do not need to remove arcs havng decorrelated phases and phase ambgutes!!

15 Temporarly Coherent Pont InSAR L 1 norm estmator How to perform L 1 norm estmaton? L 1 norm estmator s to fnd as follows: ˆx xˆ arg mn x bax 1 A h lml,,, m V W mnmze h V lml,,, m lml,,, m Aj j Soluton by teratvely reweghted least squares used n [6] for robust SBAS Soluton by lnear programmng [6] Lauknes, T. R., Zebker, H.A. and Larsen Y. (2011). IEEE Transactons on Geoscence and Remote Sensng, 49,

16 Temporarly Coherent Pont InSAR L 1 norm estmator: Soluton by lnear programmng mnmze h V lml,,, m lml,,, m Aj j mnmze f h V lml,,, m subject to f l, m, l, m Aj 0 j Wth any lnear programmng software package, t can be solved easly. mnmze f h subject to -f A f V lml,,, m l, m, l, m j j

17 Temporarly Coherent Pont InSAR The performance of the L 1 norm estmator? Even though the arc contans decorrelated phases as well as phase ambgutes, the L 1 norm estmator can precsely resolve the defo. rate!

18 Case study Data: 38 Envsat/ASAR mages acqured from 2003 to nterf. selected wth baselne thresholds: 250day,150m and 300Hz Tapa, Co Ta & Coloane (Macau)A (Many buldngs have been put up )

19 Offset devaton (0.15) Coherence (0.5) ADI (0.6) AMMR (0.25) Case study Image par based methods: TCP selecton Image based methods: ADI: Ampltude Dsperson Index AMMR: Ampltude Mad Medan Rato

20 Case study LS estmator on TCPs selected by offset devaton L 1 norm estmator on TCPs selected by AMMR Results Consstent wth ground measurements provded by DSCC of Macau

21 Case study: TCPInSAR wth hgh resoluton data Data 23 TSX SAR data from Aprl 29, 2009 to November 11, 2010 Baselne threshold: 15m, 250d 15m: No external DEM s needed!

22 Case study: TCPInSAR wth hgh resoluton data The LOS deformaton rate s up to 52 mm/yr The result has been valdated by benchmarks and CRs The work s done n collaboraton wth Guoxang Lu of SWJT Unv. Chna The feld work was performed by SWJT Unv.

23 Concluson TCPInSAR s a promsng tool for deformaton montorng on changng landscapes wth mult temporal SAR data. TCPInSAR can dentfy both persstently and partally coherent ponts Offset devaton or Ampltude Mad Medan Rato (AMMR) TCPInSAR can estmate lnear deformaton rate (for partally coherent ponts) and deformaton tme seres (for persstently coherent ponts) wth no need of phase unwrappng L 2 norm estmator wth ambguty detector L 1 norm estmator

24 Contact: Thanks! Questons?